I'm asking on behalf of my friend.
She has a full-time job at a university, and she worked for a month during summer at another company in a form of an at-will employment.
There was no formal contract, although she signed a certain document specifying the conditions of employment, which states in itself that it is not a contract.
After she stopped working at the new company and came back to the university, she realized that the signed document stated the condition that she should not receive salary from her original employer (the university) while working at the company. Since she was unaware of this condition, the university had already paid her salary, which potentially brings a dual employment issue.
Since she never singed a contract, it's technically not a breach of contract, but she did sign a document which stated the condition of at-will employment.
She seems to have inquired both the university and the company whether she can return her salary for the period or change her status from employment to 'visiting'(company) or 'break'(university), but seems to have been rejected.
Looking from the company's side (since the university is abroad), could this be a legal problem?